U.S. patent number 7,794,044 [Application Number 11/047,674] was granted by the patent office on 2010-09-14 for ink jet printing apparatus.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Daisaku Ide, Akiko Maru, Atsuhiko Masuyama, Hitoshi Nishikori, Hiroshi Tajika, Hideaki Takamiya, Takeshi Yazawa, Hirokazu Yoshikawa.
United States Patent |
7,794,044 |
Yoshikawa , et al. |
September 14, 2010 |
Ink jet printing apparatus
Abstract
A plurality of ejection portions are divided into groups, each
containing at least one ejection portion, so that the suction-based
recovery operation can be performed for each group independently.
Since the number of ejection portions contained in each group
differs, if an ink flow resistance varies among the different
groups, simultaneous suction-based recovery operations can be done
by using a common suction pump, without having to sequentially
perform the suction-based recovery operations under an optimum pump
driving condition. For this purpose, inner diameters of a plurality
of ink discharge tubes running from a plurality of cap units, which
cap a plurality of print head units having different numbers of
ejection portions, to the common pump are differentiated. This
allows different flows to be produced in different ink discharge
systems, thus generating desirable ink flows for individual ink
supply systems.
Inventors: |
Yoshikawa; Hirokazu (Kawasaski,
JP), Tajika; Hiroshi (Yokohama, JP),
Nishikori; Hitoshi (Inagi, JP), Ide; Daisaku
(Tokyo, JP), Yazawa; Takeshi (Yokohama,
JP), Masuyama; Atsuhiko (Tokyo, JP), Maru;
Akiko (Kawasaki, JP), Takamiya; Hideaki (Tokyo,
JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
34824157 |
Appl.
No.: |
11/047,674 |
Filed: |
February 2, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050174382 A1 |
Aug 11, 2005 |
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Foreign Application Priority Data
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Feb 6, 2004 [JP] |
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2004-031330 |
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Current U.S.
Class: |
347/29;
347/30 |
Current CPC
Class: |
B41J
2/16532 (20130101) |
Current International
Class: |
B41J
2/165 (20060101) |
Field of
Search: |
;347/24,29,30,32 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2000-153622 |
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Jun 2000 |
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JP |
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2001-138552 |
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May 2001 |
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JP |
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2001-205825 |
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Jul 2001 |
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JP |
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2002-205416 |
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Jul 2002 |
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JP |
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Other References
Japanese Office Action in Appln. No. 2004-031330, Japanese Patent
Office, (Jul. 17, 2009). cited by other .
English Translation of an Official Notice of Rejection in Appln.
No. 2004-031330, Japanese Patent Office, mailed Jul. 17, 2009.
cited by other.
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Primary Examiner: Vo; Anh T. N.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. An ink jet printing apparatus comprising: a print head unit
having a plurality of ejection portions; a first cap for capping a
first ejection group including a first number of ejection portions
out of the plurality of ejection portions; a second cap for capping
a second ejection group including a second number, greater than the
first number, of ejection portions out of the plurality of ejection
portions; a first tube communicating with said first cap; a second
tube communicating with said second cap; and a suction pump
provided common to said first and second tubes for generating a
negative pressure in said first and second caps, wherein an inner
diameter of said second tube is larger than that of said first tube
so that an amount of ink sucked out from each ejection portion
included in the first ejection group is equal to an amount of ink
sucked out from each ejection portion included in the second
ejection group when ink is sucked out from the first and second
ejection groups by said first and second caps.
2. An ink jet printing apparatus according to claim 1, wherein each
of the first tube and second tube have a flexible portion in at
least a part thereof, and the suction pump comprises a tube pump
that performs the suction operation by pushing and squeezing the
flexible portion.
3. An ink jet printing apparatus according to claim 1, further
comprising means for controlling the apparatus to perform a
recovery operation by sucking out ink from a plurality of ink
ejection portions, wherein, prior to performing the recovery
operation, the plurality of ink ejection portions are made to
perform ink ejections not associated with a printing operation, and
according to a temperature rise characteristic observed during the
ink ejections, a decision is made as to whether the recovery
operation should be performed simultaneously for all of the
plurality of ink ejection portions or for each group
independently.
4. An ink jet printing apparatus according to claim 1, further
comprising: a first atmosphere opening valve capable of linking the
inside of said first cap to the atmosphere when the first ejection
group is capped by said first cap; and a second atmosphere opening
valve capable of linking the inside of said second cap to the
atmosphere when the second ejection group is capped by said second
cap, wherein the ink is sucked out from one of or both of the first
and second ejection groups by controlling the first and second
atmosphere opening valves.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printing apparatus and
more particularly to a construction of a print head used in a
serial scan type ink jet printing apparatus capable of high quality
printing and to a maintenance method thereof.
2. Description of the Related Art
The ink jet printing method is a system for transforming input
image data into an output image using a liquid ink, so that a
maintenance technology for a print head that ejects ink becomes
very important. Major problems that require maintenance are briefly
explained here.
(a) The print head generally has a plurality of nozzles to enhance
a printing speed and resolution (unless otherwise specifically
noted, the nozzle generally refers to an ink ejection opening, an
ink path communicating with the ink ejection opening and an element
for generating an energy to eject ink). Depending on input image
data, there may occur nozzles that are not used for ink ejection
during a printing operation. In such nozzles ink solvent evaporates
from the ejection opening, increasing an ink viscosity in the
ejection opening or the ink path. Thus, when a normal ink ejection
energy is applied to activate these nozzles again, they may fail to
eject ink properly and stably.
(b) Ink droplets ejected from the nozzles during the printing
operation include main ink droplets and fine ink droplets (also
called mist), and the fine ink droplets may adhere to peripheries
of the ink ejection openings of the print head. The adhering ink
may in turn pull the main ink droplets being ejected out of the
nozzles, resulting in the ink droplets being deviated from an
intended direction, i.e., degrading a projection linearity of the
main ink droplets.
(c) If there are bubbles in an ink reservoir in the print head,
i.e., in the ink path deep in the nozzle or a common ink chamber
communicating with the ink path, a gas that has migrated through
the material making up the nozzles and the print head may be
trapped in the bubbles, thereby inflating them. The bubbles may
also become inflated as the temperature increases during the
printing operation. This prevents a smooth supply of ink from an
ink source, resulting in an ink ejection failure.
To solve the above problems (a) to (c), the following maintenance
techniques may be adopted.
(A) Depending on the time during which the ink ejection has not
been performed and on the environment, a predetermined amount of
ink is ejected to discharge viscous ink. This is done apart from
the ink ejection operation that is performed to form an image on a
print medium (this operation is referred to as a preliminary
ejection).
(B) The number of times that the ink has been ejected from the
nozzles is counted, and when the count value exceeds a
predetermined value, a surface of the print head formed with
ejection openings (referred to as an ejection face) is wiped by a
wiping member (such as a blade) made of an elastic material such as
rubber to remove the adhering ink from the ejection face (this
operation is called a wiping).
(C) A suction force is applied to the ejection face as by a pump at
a predetermined timing to suck out ink from the ejection openings
to forcibly draw out ink from inside the ejection openings for the
recovery of an ink ejection performance (this operation is referred
to as a suction-based recovery operation). In a construction in
which the print head and an ink tank as an ink source are separably
combined so that the ink tank can be replaced, when the ink tank is
separated for replacement, an ink supply system is open admitting a
gas (air). Some apparatus perform the above-mentioned suction-based
recovery operation after the ink tank is replaced, to remove the
gas from the ink supply system.
Here, the wiping operation and the suction-based recovery operation
will be explained briefly.
FIG. 1A and FIG. 1B show a print head as seen from its ejection
face and side. Reference number 1101 represents a blade made of
rubber to perform wiping, 1102 the ejection face, 1103 ejection
openings, 1104 adhering ink, and 1105 a wiping direction. The
wiping is an operation that, as shown in the figures, involves
moving the blade 1101 in the direction of arrow 1105 while holding
it in contact with the print head, thereby wiping the adhering ink
1104 off the ejection face 1102 by the blade.
The suction-based recovery operation on the other hand generally
involves having a cap of rubber pressed against the ejection face
1102 to form a hermetically enclosed space therein and operating a
suction pump communicating to the cap to generate a negative
pressure to suck out ink from the ejection openings or nozzles 1103
of the print head into the cap so that the ink drawn out is
discharged through an ink discharge tube connected to the suction
pump.
The suction pump may be of a tube pump type which comprises a
holding member formed with a curved surface along which to hold a
flexible ink discharge tube, a roller capable of pressing the ink
discharge tube against the holding member, and a rotatable roller
support supporting the roller. That is, by rotating the roller
support in a predetermined direction, the roller is pressed against
and flattens the ink discharge tube as it rotates over the holding
member. As a result, a negative pressure is created in the enclosed
space in the cap, sucking out ink from the nozzles which is then
drawn into the ink discharge tube and the suction pump. The Ink is
further moved toward an appropriate member (a waste ink holding
member such as an absorbent).
In today's ink jet printing apparatus on which there are growing
demands for higher print quality and speed, the number of inks used
and the number of nozzles arrayed in the print head are
significantly greater than those of several years ago. Thus, the
maintenance technology for the print head assumes a growing
importance.
Now, a current trend for higher image quality in the ink jet
printing apparatus is briefly described.
Conventionally, in the ink jet printing apparatus a color
reproduction is made basically by a subtractive color mixing using
three primary colors, yellow, magenta and cyan. For an improved
image quality, some printing apparatus use a black ink in addition
to the three primary color inks to represent a high contrast;
others use light inks with lower colorant contents (light cyan ink
and light magenta ink) to improve color tone; and others introduce
an ink droplet atomizing technology to reduce a granular impression
of an output image.
For an even further improvement in image quality, a variety of
technologies are being developed, such as one using special inks
(color inks other than cyan, magenta and yellow inks) that cover a
range of color or gamut that cannot be expressed by the above six
color inks, or one using color pigment inks that make for an
improved fastness of an output image, or one using a liquid that,
when applied to a print medium before or after ink is applied,
improves a glossiness.
One such ink let printing apparatus for improving the image quality
is available (for example, see Japanese Patent Application
Laid-open No. 2001-138552) which, in addition to black, cyan,
magenta, yellow, light cyan and light magenta inks, uses an orange
ink lying at an intermediate angle area between yellow and magenta
and a green ink lying between yellow and cyan to widen the color
range that can be reproduced.
SUMMARY OF THE INVENTION
When multiple kinds of inks are used for improved image quality, as
described above, ejection portions corresponding to the multiple
colors are provided. In this case, if a single cap is made to cover
the whole ejection portions for the recovery operation, the
suction-based recovery operation is executed uniformly for all the
ejection portions, consuming ink more than necessary.
Let us consider a configuration in which a print head and an ink
tank are separably combined to allow for ink tank replacement and
in which the suction-based recovery operation is performed after
the ink tank is replaced. In this case, each time an ink tank of
one color is replaced, the ink suction is also performed on those
ejection portions that correspond to other color inks for which the
associated ink tanks have not been replaced. As a result, inks of
other colors are wasted. This problem becomes more salient as the
number of kinds of inks increases. This configuration therefore is
not advantageous when a number of different ink colors are used as
in the above case.
To cope with this problem, the inventors of this invention have
introduced a suction cap construction in which a plurality of
ejection portions are divided into groups, each of which includes
one or more ejection portions and can undergo the suction-based
recovery operation independently of other groups. This suction cap
construction is intended to allow the suction-based recovery
operation to be executed at an optimum timing for each ejection
portion that is determined by the way the user prints, such as a
content of image to be printed and a print mode. With this
arrangement, the wasteful ink consumption can be reduced which
would otherwise be caused by a single-mode recovery operation
performed uniformly for all ejection portions after the ink tank
replacement and by an execution of the suction-based recovery
operation at too early a timing. Not only can this arrangement
reduce the overall consumption of ink but it can also prevent an
increase in the size of a waste ink holding member and therefore
the printing apparatus itself.
However, if the number of ejection portions included in each group
and the configuration of the ink supply system leading to the
associated ink tank (piping length and route) differ among the
different groups, the ink flow resistance caused by an external
pressure variation (due to the action of suction) changes from one
ink supply system to another As a result, the negative pressure and
the ink flow to achieve an optimum suction for each ejection
portion do not match among the groups.
In the apparatus in which the above grouping is made so that the
cap and ink discharge tube are provided for each group, if the
suction pump is shared from the standpoint of reducing the size of
the apparatus, the negative pressure and the ink flow produced by a
predetermined quantity of pump drive are essentially equal in all
caps or discharge tubes. Therefore, to generate an optimum negative
pressure and ink flow for each group or for the ejection portions
included in each group requires changing the pump driving condition
to make it optimum for a particular ejection portion, executing the
suction-based recovery operation for that particular ejection
portion and repeating this process successively for the remaining
ejection portions. This means that the time taken by the
suction-based recovery operation increases with the number of ink
kinds or ejection portions. During that recovery operation the
printing operation has to be halted, lowering the printing
throughput and giving unwanted stresses to the user.
To solve these problems, the present invention provides an ink jet
printing apparatus capable of performing a recovery operation by
sucking out ink from a plurality of ink ejection portions, the ink
jet printing apparatus comprising: a suction means common to the
plurality of ink ejection portions; and a means interposed between
the plurality of ink ejection portions and the suction means in
such a way that the suction operation can be performed on each
group of one or more of the ink ejection portions, the means being
adapted to generate different suction flows for different groups
when the recovery operation is performed.
With this invention, a plurality of ejection portions are divided
into groups so that each group includes one or more ejection
portions and that the suction operation can be performed
individually for each group. When the suction-based recovery
operation is performed, this invention makes an arrangement to
produce different ink flows for different groups during the suction
operation so that the ink supply systems leading to the plurality
of ejection portions can have essentially equal ink flows. As a
result, simultaneous suction-based recovery operations on all
ejection portions can be performed in a suitable condition. This in
turn ensures an effective recovery operation, reducing the suction
time to a minimum required, eliminating unwanted stresses on the
user.
The above and other objects, effects, features and advantages of
the present invention will become more apparent from the following
description of embodiments thereof taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B illustrate how a wiping operation is performed on a
print head of an ink jet printing apparatus for maintenance;
FIG. 2 is a perspective view showing a mechanism portion of the
printing apparatus according to one embodiment of this
invention;
FIG. 3 is a perspective view showing an ink tank being mounted on a
head cartridge applied to one embodiment of this invention;
FIG. 4 is an exploded perspective view of the head cartridge
applied to one embodiment of this invention;
FIG. 5 is a schematic diagram showing a construction of the print
head used in the head cartridge of FIG. 4 in which a print head
unit featuring a fast full-color printing and a print head unit
featuring a high quality printing are separated;
FIG. 6 is a perspective view of a suction-based recovery unit
making up a cleaning unit of FIG. 2;
FIG. 7 is a cross-sectional view taken along the line VII-VII of
FIG. 6, showing the suction-based recovery unit and its associated
components;
FIG. 8 is a block diagram schematically showing an overall
configuration of a control system in the printing apparatus of FIG.
2;
FIG. 9 is a flow chart showing an example sequence of the
suction-based recovery operation performed in one embodiment of
this invention;
FIG. 10 illustrates an outline of an ink supply system from an ink
tank to nozzles in one embodiment of this invention;
FIG. 11 is a conceptual diagram showing an ink flow generated by a
pump in one ink supply system; and
FIG. 12 is a diagram showing how an inner diameter of an ink
discharge tube is determined to obtain an appropriate ink flow in
each of the ink supply systems.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Now, referring to the accompanying drawings, an embodiment of this
invention will be described in detail.
(Mechanical Construction of Ink Jet Printing Apparatus)
FIG. 2 is a perspective view showing an ink jet printing apparatus
of this embodiment, with its enclosure removed to expose its
internal mechanism. The printing apparatus body of this embodiment
may be classified by function into a paper supply unit, a paper
transport unit, a paper discharge unit, a carriage unit, a cleaning
unit and an enclosure unit. Since this invention concerns mainly
the suction-based recovery operation, our explanation focuses
mainly on the construction of the cleaning unit.
Cleaning Unit
The cleaning unit comprises a suction-based recovery unit, which
includes a pump M5000 for cleaning a print head (described later)
and a cap M5010 for keeping the print head from drying, and a
wiping unit including a blade M5020 for cleaning an ejection face
of the print head.
The cleaning unit is provided with a dedicated cleaning motor
E0003. The cleaning motor E0003 has a one-way clutch (not shown),
which enables the motor to drive the pump when the motor rotates in
one direction and, when the motor rotates in the opposite
direction, enables the motor to raise or lower the cap M5010 to
close or open the ejection face of the print head and subsequently
to move the blade M5020 to wipe clean the ejection face of the
print head.
Although its detailed construction is described later by referring
to FIG. 6 and FIG. 7, the pump M5000 activated by the cleaning
motor E0003 has a tube pump construction in which a pump roller
squeezes the ink discharge tube connected to the cap M5010 to
generate a negative pressure in the cap. That is, with the cap
M5010 kept in hermetic contact with the ejection face of the print
head, activating the pump M5000 causes ink to be sucked out from
the ejection openings of the print head.
Inside the cap M5010 an absorbent M5011 is placed to reduce the
amount of ink remaining on the ejection face of the print head
after being sucked out of the nozzles. To remove the ink that was
sucked out into the cap M5010 and to prevent the ink from
solidifying and thereby prevent the associated problems, the pump
M5000 is operated with the cap M5010 open to the atmosphere to draw
the residual ink out of the cap M5010 by suction. The ink drawn out
by the pump M5000 is absorbed as waste ink in a waste ink absorbent
(not shown) provided at an appropriate location, such as at a
bottom or back of the apparatus, where it is retained.
When the cap M5010 Is lowered to part from the ejection face of the
print head, the blade M5020 is moved through an open space directly
below the ejection face in a direction perpendicular to the scan
direction of the carriage M4000 to wipe clean the ejection face of
the print head. A plurality of blades M5020 are provided which
include one for cleaning the nozzles and the surrounding area of
the print head H1001 and one for cleaning the entire ejection face.
When the carriage M4000 reaches the farthest end of the stroke, it
engages a blade cleaner M5060 by which the blade M5020 itself is
removed of the adhering ink.
Other Mechanisms
The paper supply unit has a mechanism to separate one sheet at a
time from the print medium stacked on a pressure plate 2010. The
paper transport unit has a transport roller M3060 and a pinch
roller M3070 that together hold and carry the supplied print medium
toward a printing area, a transport motor E0002 for driving the
transport roller and pinch roller, and a platen M3040 that supports
the print medium in the printing area. The paper discharge unit has
a discharge roller M3110 to discharge the printed medium from the
printing area and a plurality of spur rollers that cooperate with
the discharge roller.
The carriage unit has a carriage M4000 on which to mount a print
medium. The carriage M4000 is supported by a guide shaft M4020 and
a guide rail M1011, the guide shaft M4020 guiding and supporting
the carriage M4000 so that the carriage M4000 can reciprocally
travel in a direction perpendicular to the transport direction of
the print medium. The carriage M4000 is driven by a carriage motor
E0001 mounted on a chassis M1010 through a timing belt M4041.
In the above construction, when an image is formed on a print
medium, a roller pair consisting of the transport roller M3060 and
the pinch roller M3070 transports and positions the print medium
with respect to the transport direction (or row direction). As to a
position in the main scan direction (or column direction), the
carriage motor E0001 moves the carriage M4000 in a direction
perpendicular to the transport direction to locate the print head
at a desired image forming position. The print head thus positioned
ejects ink onto the print medium in response to a signal from an
electric control board E0014. Although the detailed construction of
the print head and the print system will be described later, the
printing apparatus of this embodiment forms an image on the print
medium by alternating a printing main scan, in which the print head
prints as the carriage M4000 scans in the main scan direction, and
a sub-scan in which the print medium is transported by the
transport roller M3060 in the transport direction.
Print Head
Next, the construction of a head cartridge H1000 applied to this
embodiment will be described. The head cartridge H1000 in this
embodiment has means for mounting a print head H1001 and an ink
tank H1900 and means for supplying ink from the ink tank H1900 to
the print head. The head cartridge H1000 is removably mounted on
the carriage M4000.
FIG. 3 shows how the ink tank H1900 is mounted on the head
cartridge H1000 applied in this embodiment. The printing apparatus
of this embodiment forms an image using eight color inks and
therefore eight independent ink tanks H1900 are provided for eight
colors. Then, as shown in the figure, each of the ink tanks is
removably mounted on the head cartridge H1000. The removing of the
ink tanks H1900 can be done with the head cartridge H1000 put on
the carriage M4000.
FIG. 4 is an exploded perspective view of the head cartridge H1000.
In the figure, the head cartridge H1000 comprises a first nozzle
substrate H1100 and a second nozzle substrate H1101, a first plate
H1200, a second plate H1400, an electric wiring board H1300, a tank
holder H1500, a flow path forming member H1600, a filter H1700, and
a silicone rubber H1800.
The first nozzle substrate H1100 and the second nozzle substrate
H1101 are silicon substrates each of which is formed on one surface
with a plurality of ink ejection nozzles by a photolithography
technique. Electric wires for supplying electricity to the nozzles,
such as aluminum wires, are formed by a deposition technique The
ink paths connected to individual nozzles are also formed by the
photolithography. Further, each of the first and second nozzle
substrates is formed on the back with an ink supply port to supply
ink to the individual ink paths.
A column of nozzles (or nozzle column) for each of different ink
colors is made up of 768 nozzles arranged at intervals of 1200 dpi
(dots/inch) in the print medium transport direction, each of which
ejects ink droplets of about 2 pico-liters. An opening area of each
nozzle is set to about 100 .mu.m.sup.2. The first nozzle substrate
H1100 and the second nozzle substrate H1101 are securely bonded to
the first plate H1200 which is formed with ink supply ports H1201
to supply ink to the first nozzle substrate H1100 and the second
nozzle substrate H1111.
Further, the first plate H1200 is securely bonded with the second
plate H1400 having openings, which has the electric wiring board
H1300 electrically connected with the first nozzle substrate H1100
and the second nozzle substrate H1101.
The electric wiring board H1300 applies an electric signal to the
associated nozzles formed in the first nozzle substrate H1100 and
the second nozzle substrate H1101 to eject ink from the individual
nozzles. The electric wiring board H1300 comprises electric wires
connected to the first nozzle substrate H1100 and the second nozzle
substrate H1101 and an external signal input terminal H1301
situated at an end portion of the electric wiring board H1300 to
receive an electric signal from the printing apparatus body. The
external signal input terminal H1301 is positioned and secured on
the back side of the tank holder H1500.
The tank holder H1500 holding the ink tank H1900 has the flow path
forming member H1600 secured thereto as by ultrasonic fusing to
form an ink path H1501 running from the ink tank H1900 to the first
plate H1200.
At the end of the ink path H1501 on the ink tank side that engages
the ink tank H1900, a filter H1700 is provided to prevent ingress
of dust from outside. The engagement portion of the filter with the
ink tank H1900 is attached with a seal rubber H1800 to prevent ink
evaporation.
Further, the tank holder unit made up of the tank holder H1500, the
flow path forming member H1600, the filter H1700 and the seal
rubber H1800 is combined, as by bonding, with the print head H1001
made up of the first nozzle substrate H1100, the second nozzle
substrate H1101, the first plate H1200, the electric wiring board
H1300 and the second plate H1400 to construct the head cartridge
H1000.
FIG. 5 shows an arrangement of nozzle groups in the print head in a
first embodiment of this invention. Here, reference number 1302
corresponds to the first nozzle substrate H1100, a print head unit
featuring a high-speed full color printing. Reference number 1303
corresponds to the second nozzle substrate H1101, a print head unit
featuring a high quality printing.
The print head unit 1302 characterized by the fast full color
printing has ejection portions 1304, 1305, 1306 to eject yellow,
magenta and cyan inks--three primary colors of colorants--to
reproduce full color by the subtractive color mixing. Each of the
ejection portions has a nozzle column with nozzles arranged in a
direction different from the scan direction 1312 of the print head
H1001 (e.g., in the transport direction of a print medium crossing
the scan direction almost at right angles) and has two nozzle
columns for each color. These two nozzle columns are shifted from
each other by one-half pitch of the nozzles in the transport
direction. In the figure, two ejection portions (each having two
columns) shown to the left of the ejection portion 1304 are not
used in this embodiment.
The print head unit 1303 characterized by the high quality printing
has ejection portions 1307, 1311 to eject a light cyan ink and a
light magenta ink to enhance the color tone of an output image, and
an ejection portion 1309 to eject a black ink to enhance a contrast
of the output image. Further, in this embodiment, to make it
possible to reproduce a color range that cannot be reproduced by
the primary colors alone--cyan, magenta and yellow--ejection
portions 1308, 1310 to eject two special inks (special ink 1 and
special ink 2) are provided. In the print head unit 1303 too, each
of the ejection portions 1307-1311 is made up of two nozzle
columns, as with the print head unit 1302.
Suction-Based Recovery Unit
FIG. 6 is a perspective view of the suction-based recovery unit and
FIG. 7 is a cross-sectional view taken along the line VII-VII of
FIG. 6 including the suction-based recovery unit. A cap M5010
forming the suction-based recovery unit of this embodiment is made
up of two cap portions M5010, M5010B that can be brought into
contact with or pressed against the ejection surface of the print
head unit 1302 having the ejection portions 1304-1306 and the
ejection surface of the print head unit 1303 having the ejection
portions 1307-1311. Further, the cap units M5010A, M5010B are
provided with atmosphere opening valves 1404, 1405 respectively,
which can individually open the spaces inside the cap units to, and
close them from, the open air. The cap units M5010A, M5010B are
connected with flexible ink discharge tubes 1402, 1403.
The suction-based recovery unit of this embodiment uses a tube pump
as the suction pump M5000 that creates a negative pressure to suck
out ink. The tube pump comprises a member 1406 having a curved
surface along which to hold the elongate portions of the flexible
ink discharge tubes 1402, 1403; a roller (not shown) capable of
pressing the elongate portions of the tubes 1402, 1403 against the
curved surface; and a roller support (not shown) rotatable about a
rotary shaft 1408 in a direction indicated by arrow 1407. That is,
rotating the roller support in the direction of arrow 1407 causes
the roller to squeeze the tubes 1402, 1403 on the curved surface of
the member 1406 as it rotates. This in turn creates a negative
pressure in the closed spaces formed by the cap units M5010A,
M5010B, drawing out ink by suction from the ejection openings of
the nozzles for each color into the tubes 1402, 1403. Then, the ink
thus drawn out is further drawn from the end of each tube toward an
appropriate member (such as a waste ink holding member).
Here, if the suction pump is provided independently for each of the
ink discharge tubes 402, 1403, the suction-based recovery unit
would become large in volume, increasing the size of the printing
apparatus and therefore the cost. In this embodiment, therefore, a
single suction pump M5000 is provided for two ink discharge tubes
1402, 1403, as described above, and is driven by the motor E0003 as
a single drive source. That is, while the cap units M5010A, M5010B,
the atmosphere opening valves 1404, 1405 and the ink discharge
tubes 1402, 1403 are provided independently for each of the print
head units 1302, 1303, the suction pump M5000 is used commonly.
The suction-based recovery operation is performed as follows. The
cap units M5010A, M5010B are simultaneously capped onto the print
head units 1302, 1303 and at the same time only the atmosphere
opening valve provided at the cap unit corresponding to the print
head unit on which one wishes to perform the suction-based recovery
operation is closed and the atmosphere opening valve provided at
the cap unit corresponding to the print head unit that does not
require the suction-based recovery operation is opened. With this
operation the desired print head unit can be chosen for the
suction-based recovery operation.
As described above, by capping the cap units M5010A, M5010B on the
ejection surfaces of the print head units 1302, 1303 and operating
the suction pump M5000, with the corresponding atmosphere opening
valve closed, to suck out ink from the inside of the cap or from
the nozzles of the print head unit 1302 and/or 1303, it is possible
to keep the ink ejection from the print head units 1302, 1303 in
good condition.
In this embodiment, the cap units M5010A, M5010B are formed
integral with the cap M5010 to enable simultaneous capping of both
the print head units 1302, 1303. Further, it is made possible to
individually open and close the atmosphere opening valve 1404
corresponding to the print head unit 1302 and the atmosphere
opening valve 1405 corresponding to the print head unit 1303, thus
allowing for an independent suction-based recovery operation for
each of the print head units. However, two separate caps may be
used to cap the associated print head units 1302, 1303
individually.
The vertical movement of the cap M5010 and the operation of the
blade M5020 can be controlled mechanically by a main cam 1420 which
has a plurality of cams on a shaft 1410, as shown in FIG. 7. That
is, cam surfaces at different locations act on a link mechanism
such as arm to produce a predetermined operation. The rotary
position of the main cam 1420 can be detected by a position sensor
such as photo-interrupter.
(Configuration of Control System in Ink Jet Printing Apparatus)
Next, the configuration of a control system in this embodiment,
i.e., a control circuit and its operation, will be explained.
Control Circuit
FIG. 8 is a block diagram schematically showing an overall
configuration of the control circuit in one embodiment of this
invention.
The printing apparatus of this embodiment comprises mainly a
printed circuit board for a carriage (CRPCB) E0013, a main PCB
E0014, a power supply unit E0015 and a front panel E0106. The power
supply unit E0015 is connected to the main PCB E0014 to supply a
variety of driving power.
The CRPCB E0013 is a printed circuit board unit mounted on the
carriage M4000 and functions as an interface to transfer signals to
and from the print head H1010 through a head connector E0101.
According to a pulse signal output from an encoder sensor E0004 as
the carriage M4000 moves, the CRPCB E0013 detects a change in
positional relation between an encoder scale E0005 and an encoder
sensor E0004 and outputs its signal to the main PCB E0014 through a
flexible flat cable (CRFFC) E0012. The CRPCB E0013 has sensors
E0102 including a temperature sensor such as thermistor to detect
an ambient temperature and an optical sensor. Information obtained
from these sensors E0102 is output to the main PCB E0014 through
the flexible flat cable E0012 together with the head temperature
information from a temperature sensor (not shown) provided in the
print head cartridge H1000.
The main PCB E0014 is a printed circuit board unit that governs an
operation and control of various parts in the ink jet printing
apparatus of this embodiment. On the printed circuit board are
mounted a CPU that performs a variety of controls including the
suction-based recovery operation control to be described by
referring to FIG. 9, and a ROM storing a program to be executed by
the CPU. The main PCB E0014 also has a paper end (PE) sensor E0007,
an automatic sheet feeder (ASF) sensor E0009, a cover sensor E0022
and a host interface (host I/F) E0017. The main PCB is also
connected with various motors, such as a carriage motor E0001 that
drives the carriage M4000 for main scan, an LF motor E0002 to carry
a print medium, a motor E0003 as a drive source for a recovery
operation of the print head H1001, and an ASF motor E0105 as a
drive source for the print medium supply operation. Further, the
main PCB receives various sensor signals E0104 representing the
mounting condition and operation state of option units, such as ink
empty sensor, media (paper) sensor, carriage position (height)
sensor, LF encoder sensor and PG sensor. The main PCB also outputs
an option control signal E0108 for controlling the operation of the
option units. Further, the main PCB E0014 is connected with the
CRFFC E0012, the power supply unit E0015 and the front panel E0106
and has an interface to transfer information by a panel signal
E0107.
For ease of user operation, the front panel E0106 is provided on
the front of the printing apparatus body and has a resume key
E0019, an LED E0020, a power key E0018 and a device I/F E0100 for
connection with peripheral devices such as digital camera.
Sequence of Suction-Based Recovery Operation
FIG. 9 shows, among various controls executed in the above
configuration, an example control sequence in performing the
suction-based recovery operation on the print head units 1302,
1303, which constitutes a main part of this embodiment.
First, with the carriage M4000 set so that the print head units
1302, 1303 oppose the cap units M5010A, M5010B respectively, the
atmosphere opening valves 1404, 1405 of the cap units M5010A,
M5010B are both closed (step S1). Next, the cap M5010 is raised to
press the cap units M5010A, M5010B against the print head units
1302, 1303 to cap their ejection faces (step S2). With these steps
taken, the print head units 1302, 1303 are both hermetically
closed.
Next, the suction pump M5000 connected to the two ink discharge
tubes 1402, 1403 is operated to perform the suction-based recovery
operation on the print head units 1302, 1303 (step S3). If at this
time the atmosphere opening valves are left open, external air is
drawn in through the atmosphere opening valves, nullifying the
suction-based recovery operation. The revolution of the suction
pump can be changed according to the purpose of the maintenance
(the volume of ink to be discharged from the print head H1001).
Next, when the predetermined suction-based recovery operation is
finished, the atmosphere opening valves 1404, 1405 are opened to
admit air into the cap units M5010A. M5010B that hermetically
closed the print head units 1302, 1303, thereby stopping the ink
from moving in the print head H1001 (step S4).
Next, with the cap M5010 lowered, the blade M5020 is moved to
perform a wiping operation to wipe residual ink droplets off the
ejection surfaces of the print head units 1302, 1303 (step S5).
Next, with the atmosphere opening valves 1404, 1405 left open, the
cap M5010 is raised (step S6). Then, with the cap units M5010A,
M5010B engaging the print head units 1302, 1303, respectively, the
suction pump M5000 is operated to cause both of the print head
units 1302, 1303 to perform the preliminary ejection (step S7). The
operation in step S7 is intended to prevent a possible
contamination of the interior of the printing apparatus which would
otherwise be caused by ink mist moving into the apparatus during
the preliminary ejection.
Next, the cap M5010 is lowered again, followed by a wiping
operation to clear residual ink droplets from the ejection surfaces
of the print head units 1302, 1303 (step S8). Then, a preliminary
ejection is performed to eject ink into the lowered cap M5010 (step
S9), thus completing a series of operations associated with the
suction-based recovery.
Performing the above operations enables both of the print head
units 1302, 1303 to be processed simultaneously by the
suction-based recovery operation. It is also possible to operate
the suction pump M5000 after step S9 to control the suction-based
operation to discharge ink from inside the cap M5010.
If one wishes to perform the suction-based recovery operation
individually on the print head unit 1302 and 1303, one of the
atmosphere opening valves 1404, 1405 needs to be closed before
proceeding to the above-mentioned sequence of operations.
Whether the suction-based recovery operation should be performed on
the print head units 1302, 1303 either simultaneously or
individually can be chosen appropriately. For example, prior to
initiating the suction-based recovery operation, a predetermined
preliminary ejection may be performed using the print head units or
each color ejection portion and temperature rise characteristics
may be measured. If no temperature rise in excess of a
predetermined threshold is detected in any print head unit or color
ink ejection portion, it is decided that there exists no trapped
air or bubble in the ink supply path that would block a smooth ink
supply. The suction-based recovery operation therefore may be
performed simultaneously on both the print head units 1302, 1303.
On the other hand, if a temperature rise in excess of the
predetermined threshold is detected in one of the print head units
or one of the color ink ejection portions, or when an ink tank of a
certain color is replaced, the suction-based recovery operation may
be performed concentratedly only on the print head unit in
question.
As described above, in this embodiment, the print head unit 1302
featuring the fast full color printing and the print head unit 1303
featuring the high quality printing are separated in the print head
H1001 so that these print head units can be processed by the
suction-based recovery operation independently of each other. This
enables the suction-based recovery operation to be performed only
on the print head unit that needs it, reducing the number of color
inks used in the recovery operation or the number of ejection
portions undergoing the recovery operation from that of full eight
colors down to that of five or three colors. This in turn reduces
the amount of ink consumed during the suction-based recovery
operation.
(Design of Suction-Based Recovery Unit)
The following description concerns a construction that enables an
appropriate suction-based recovery operation to be performed either
simultaneously or separately on the print head units 1302,
1303.
FIG. 10 schematically shows an ink supply system running from ink
tanks to ink ejection nozzles.
Denoted 1601-1608 in the figure are filters that are connected to
the ink tank situated above That is, the filters 1601-1608 are
connected to the ink tanks H1900 situated above that accommodate
yellow ink, magenta ink, cyan ink, light cyan ink, special ink 1,
black ink, special ink 2 and light magenta ink.
Portions indicated by 1609-1616 in the figure are supply paths to
supply inks from individual ink tanks. Further, portions
represented by reference numbers 1619-1626 are ink chambers to
stably distribute and supply ink to the ejection portions 1304-1311
of the associated color inks and are equal in shape and dimension.
Denoted 1617 and 1618 are also ink chambers that correspond to the
two ejection portions which in FIG. 5 are shown to the right of the
ejection portion 1306 and not used in this embodiment. These two
ink chambers are not connected with ink pipes.
That is, the ink path for the print head unit (for cyan, magenta
and yellow) 1302 featuring the fast full color printing is formed
by the filters 1601-1603, the supply paths 1609-1611 and the ink
chambers 1619-1621. The ink path for the print head unit (for
black, light cyan, light magenta, special ink 1 and special ink 2)
1303 featuring the high quality printing is formed by the filters
1604-1608, the supply paths 1612-1616 and the ink chambers
1622-1626.
Here, in the first embodiment of this invention, how much ink flow
should be generated in each of the ink discharge tubes 1402, 1403
according to the purpose of the suction-based recovery operation
will be explained.
The suction-based recovery operation is performed to deal with the
problem (c) described earlier That is, the suction-based recovery
is performed when it is desired to remove bubbles lying in the ink
paths, ink chambers and nozzles or to replace viscous ink near the
ejection openings resulting from the evaporation of solvent with
new ink. The suction-based recovery is also performed when the ink
in the ink tank is consumed completely or when the ink supply paths
and ink chambers are to be refilled with ink after the ink supply
system is opened during the ink tank replacement.
In these cases, the ink flow in the ink supply path and the ink
chamber is an important factor to be considered because too small
an ink flow may result in a large air space remaining in the ink
chamber during refilling and because bubbles present in the ink
chamber hardly move and thus are not easily removed. On the other
hand, too large an ink flow may result in outer air being drawn in
from a joint between the ink tank H1900 and the print head H1001,
undesirably increasing bubbles in the ink chamber.
In this embodiment in which there are no large differences in the
size of the ink supply path and ink chamber between different
systems, when each system is seen as an independent system, it can
be assumed that a sufficient ink flow for the suction-based
recovery operation is almost uniquely determined However, it must
be noted in this embodiment that the print head unit 1302 featuring
the high-speed full color printing has three systems of ink supply
path and ink chamber, one for each of cyan, magenta and yellow, and
that the print head unit 1303 featuring the high quality printing
has five systems of ink supply path and ink chamber, one for each
of black, light cyan, light magenta, special ink 1 and special ink
2. Therefore, the total ink flows that are considered sufficient in
these print head units for the suction-based recovery operation
differ.
In this embodiment therefore, when the suction-based recovery
operation is performed on the print head unit 1302 by the suction
pump M5000, the ink flow in the ink discharge tube 1402 is set to
three times the ink flow required in one system. As for the
suction-based recovery operation on the print head unit 1303, the
ink flow in the ink discharge tube 1403 is set to five times the
ink flow required in one system.
As described above, in order to produce ink flows three times and
five times the ink flow required in one system when simultaneous
suction-based recovery operations are performed by a single drive
system, this embodiment differentiates effective cross-sectional
areas or, more specifically, inner diameters of the ink discharge
tubes 1402 and 1403 having circular cross-sections, thus generating
different ink flows.
Now, how the diameters of the ink discharge tubes 1402, 1403 are
determined in this embodiment will be explained.
FIG. 11 conceptually shows an ink flow in one system generated by a
pump.
An area 131 marked with inclined lines represents an area where the
ink flow is too small to completely fill the ink chamber with ink.
An area 132 marked with dots represents an area where the ink flow
Is so large that external air is drawn in from a joint between the
ink tank H1900 and the print head H1001, undesirably increasing
bubbles in the ink chamber. An area 133 marked with inclined lines
represents an area where an object can be suitably achieved without
causing the above problems. Therefore, it is strongly desired that,
in either of the print head units 1302 and 1303, an ink flow which
falls in the range of the inclined-line area 133 be produced in
each system during the suction-based recovery operation by each of
the ink discharge tubes 1402, 1403.
In this embodiment, the Inner diameter of the tube 1403 on the
print head unit 1303 having five systems of ink path and ink
chamber is first set to 3.5 mm. Then, the drive quantity for the
suction pump M5000 or the PG motor E0003 is determined to satisfy
the condition that the ink flow in one system falls in the area
133. Then, using the same drive quantity, the inner diameter of the
ink discharge tube 1402 is determined such that the ink flow in one
system on the print head unit 1302 having three systems of ink path
and ink chamber falls in the area 133.
FIG. 12 is a conceptual diagram showing different ink flows
produced in a single system for different inner diameters of tube
when the recovery operation is executed on the print head unit
having three systems by using the same drive quantity that was
determined for the print head unit having five systems. A curve A
represents a suction negative pressure waveform for a tube inner
diameter of 3.0 mm, a curve B represents a waveform for the same
tube inner diameter of 3.5 mm as that of the five-system side, and
a curve C represents a waveform for a tube inner diameter of 2.5
mm.
For the curve B that was obtained when the tube was set to the same
inner diameter of 3.5 mm as that of the five-system side, the ink
flow produced on the five-system side was appropriate but too large
on the three-system side, so that external air was drawn in from a
joint between the ink tank and the print head, undesirably
increasing bubbles in the ink chamber. For the curve C where the
tube inner diameter was set to 2.5 mm, it was observed that the ink
flow was too small to fill ink into the empty ink chamber. For the
curve A where a tube 2.5 mm in inner diameter was used, the suction
operation could be performed appropriately in any system without
causing the above problems, Therefore, for the tube 1402 on the
print head unit 1302 that features the high-speed full color
printing and has three systems of ink path and ink chamber, a tube
inner diameter of 3.0 mm was chosen.
Although the tube diameter on the print head unit 1302 having three
systems has been determined here by taking the print head unit 1303
having five systems as a drive reference, the procedure may of
course be reversed by taking the tube diameter on the print head
unit 1302 having three systems as the drive reference and then
determining the tube diameter on the print head unit 1303 having
five-systems.
(Others)
In the ink set of the above embodiment, since inks of different
colors contact or mix together in the cap or ink discharge tube, it
is desired that a reaction does not occur. That is, it is desired
that no reaction occurs in either one of ink sets, i.e., the ink
set including yellow, magenta and cyan inks and the ink set
including black, light cyan, light magenta, special 1 and special 2
inks. For this reason, this embodiment used dye-based inks for
eight colors. However, if there is no adverse effect on the ink
ejection performance and maintainability when different kinds of
inks contact and mix together, both of the dye-based inks and
pigment-based inks may be used. Further, there is no limitations on
the color used. If a plurality of kinds of ink that do influence
the ink ejection or maintenance characteristics are used, it is
possible to classify those inks that do not react upon contact as
one group and to form an ink discharge system for that group
including a cap and ink discharge tube.
As for the number of ink discharge systems and the kinds (colors)
and numbers of inks and ejection portions that correspond to one
ink discharge system, there is no limitation and any appropriate
selection can be made for size and cost reduction.
In an ink jet printing apparatus capable of performing a recovery
operation by sucking out ink from a plurality of ejection portions
using a common suction means, one or more ejection portions are
gathered into groups so that ink can be sucked out from any group
of ejection portions. An arrangement is made to produce different
ink flows in different groups of ejection portions during the
suction operation in order to ensure that, when the recovery
operation is performed, substantially the same flow can be produced
in each of a plurality of ink supply systems leading to the
plurality of ejection portions.
In other words, when simultaneous suction-based recovery operations
are performed in a conventional apparatus, desirable suction-based
recovery operation cannot be achieved for all of a plurality of ink
supply systems. This is because the conventional apparatus have an
ink supply construction in which an ink flow resistance subjected
to an external pressure variation may vary from one ink supply
system to another. This occurs when the number of ejection portions
or ink supply systems grouped together differ from another group
(i.e., in a construction like the above-described embodiment, there
are three ink supply systems on the print head unit 1302 and five
ink supply systems on the print head unit 1303). In this invention,
however, since different ink flows can be produced during the
suction operation among different groups of ejection portions,
substantially equal flows can be produced in each of the plurality
of ink supply systems leading to the plurality of ejection
portions. As a result, appropriate suction-based recovery
operations can be performed simultaneously on all ejection portions
under desirable conditions.
This invention is not limited to a configuration in which the
number of ejection portions or ink supply systems grouped together
differs from another group. The invention can be applied widely and
effectively as long as the ink supply structure is such that
different ejection portions have different number of nozzles or
different nozzle diameters, that the structures of the plurality of
ink supply systems differ, or that different ejection portions
exhibit different ink flow resistances when subjected to external
pressure variations.
In the above example, a tube pump has been used to perform a
suction operation by changing a volume in the tube by flattening
and squeezing the tube To differentiate the volume change among
different ink supply systems during the suction-based recovery
operation on the print head units, the ink discharge tubes of
different inner diameters, essentially circular and connected to
the cap units, are used. However, in this case, the requirement of
differentiating the ink flow during the suction operation among the
groups of discharge portions does not limit the configuration to
the one that uses the ink discharge tubes of different inner
diameters, but allows for an adoption of other configurations in
which effective cross-sectional areas of ink flows and/or flow
rates are properly differentiated among the different groups of
ejection portions. Further, as a suction means, a piston pump and a
gear pump may be used instead of the tube pump that performs
suction by a volume change.
The present invention has been described in detail with respect to
preferred embodiments, and it will now be apparent from the
foregoing to those skilled in the art that changes and
modifications may be made without departing from the invention in
its broader aspects, and it is the intention, therefore, that the
appended claims cover all such changes and modifications.
This application claims priority from Japanese Patent Application
No. 2004-031330 filed Feb. 6, 2004, which is hereby incorporated by
reference herein.
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